The changes in the specific growth rate of Streptococcus sanguis limiting glucose concentrations was examined. When cells from an exponetially growing culture were used as an inoculum, we could not obtain a sufficient difference in growth rate with glucose concentration to get a reliable estimate of the saturation constant. The rate of disappearance of glucose in these cultures was inversely and highly correlated with the rate increase in cell mass of the cultures. The true saturation constant for glucose limiting the growth of S. sanguis seems lower than previously thought. Different methods for the determination of DNA in whole cells have been tried to obtain more reliable estimates of the growth rates of the cultures. S. sanguis has been sucessfully immobilized in calcium alginate cells and the methods for the standardization of the cell entrapped cells have started.